IgA nephropathy (IgAN) is the most common type of glomerulonephritis worldwide. 15-40% of individuals diagnosed with IgAN, including children, will eventually progress to chronic renal insufficiency (CRI) and end stage renal disease (ESRD). The study is to evaluate the safety and benefits of MMF in patients with IgAN who have been pre-treated (and continue to be treated) with angiotensin converting enzyme inhibitors (ACEi) and fish oil supplements (FOS).